Conventionally, there is used a card reader, as an example of a magnetic information processing device, which is for reading magnetic information recorded in a card, and for newly writing magnetic information into a card, by way of making a magnetic head contact a magnetic stripe prepared on the card, and slide on the magnetic stripe.
Sometimes, a magnetic head installed in a card reader may pick up a foreign magnetic noise and the like, coming from a surrounding environment, as a magnetic signal. In other words, sometimes such a magnetic noise may have a negative impact on the magnetic head so that magnetic information cannot correctly be read out. Then, for example, in Patent Document 1, there is described a magnetic head provided with a card detection circuit in order to detect a card being drawn in, by the intermediary of a changeover switch, the magnetic head being for a card reader that implements a countermeasure against a foreign magnetic noise. If an analog signal generated by the magnetic head exceeds a threshold value that has been set, when a card-like medium is drawn in, the card detection circuit outputs a signal notifying of a card being detected (detection output signal), and transfers the signal to a higher-level device. At a time when the higher-level device receives the detection output signal, the changeover switch operates to shift a status of the magnetic head device from a standby state to a working state.